System of control



A. J. HALL AND L. M. PERKINS.

SYSTEM OF CONTROL.

APPLICATION FILED.AUG.4. 191s.

Patented Dec. 10,1919.

2 SHEETS-SHEET I.

77-01 leg Overload INVENTOR ArThurJ Hall, and

WITNESSES:

Laultgqce M. Prk ms.

A'TTORNEY A. J. HALL AND L. M. PERKINS.

SYSTEM OF CONTROL. APPLICATION FILED AUG-M1916.

1,324,814, Patented Dec. 16,1919.

{SHEETS-SHEET 2. L

Accelerafion.

a a a v, I x Grow) wnusssss: I

Y INVENTOR w A/f/Hl/J Hall, and

r LaurgqceM. Perkins.

UNITED STATES PATENT OFFICE. ARTHUR J. HALL ANL LAURENCE PERKINS, OFWILKINSBURG, PENNSYLVANIA, ASSIGNORS T0 WESTINGHOUSE ELECTRIC ANDMANUFACTURING COMPANY, A

CORPORATION OF PENNSYLVANIA.

SYSTEM OF CONTROL.

Specification of Letters Patent.

Patented Deere, 1919.

railway motors and the like during both accelerating and theregenerative periods.

Various systems of direct-current regenerative control have beenproposed wherein combinations of variable resistors and auxiliarysources of energy in connection with the main field windings have beenemployed for effectingregenerative operation of the machine, forexample, the system disclosed in a co-pending application of R. E.Hellmund, Serial No. 4%,448, filed August 9, 1915, patented April 1,1919, No. 1,298,706, and assigned to the Vestinghouse Electric &Manufacturing Company, wherein a resistor is connected in series-circuitrelation with the regenerating armature across the supply circuit, and aseries circuit, including the main field winding or windings and anauxiliary source of energy, is connected across the resistor.Furthermore, it has been previously proposed to employ motor-generatorsets or the like as machines of the so-called booster type for effectingacceleration of the main machines, with relatively low or substantiallyzero rheostatic losses and also to effect predetermined regenerativeopera tion of the main machine.

One object of our present invention is to provide means which shall berelatively simple and inexpensive in construction and effective andreliable in operation-for automatically maintaining a predeterminedratio between the supply-circuit voltage and the voltage of one or morecoasting dynamoelect-ric machines, whereby the system is maintained insubstantially instant. readiness to effect either acceleration orregeneration in accordance with the selection of the train-operator.

More specifically stated, it is an object of our invention to soautomatically govern the excitation of the main machines under coastingconditions, and the concurrent excitation of a plurality of auxiliaryregulating machines that the system is always ready to practicallyinstantly inaugurate accelerating or regenerative action at the will ofthe train-operator.

()ther minor objects of our invention will become evident from thesubsequent detailed description and are fully set forth in the appendedclaims.

Certain novel features of the hereinafterdescribed system are the jointinvention of R. E. Hellmund, A. J. Hall and L. M. Perkins, and are setforth and claimed in a copending application, Serial No. 113,130, filedAug. at, 1916, and assigned to the Westinghouse Electric &ManufacturingCompany.

Our invention may best be understood by reference to the accompanyingdrawings, wherein Figure 1 is a diagrammatic view of the main circuitsand of a portion of the auxiliary governing circuits embodying ourinvention; Fig. 2 and Fig. 3 are diagrammatlc views of the greaterportion of the auxiliary governing circuit connections for manipulatingthe various pieces of apparatus that are shown in Fig. 1; Fig. a is adetailed diagrammatic view of a complete main-circuit switch, asemployed in the system of Fig. 1; and Figs. 5 and 6 are simplifieddiagrammatic views showing the initial main-circuit connections foracceleration and regeneration, respectively.

Referring to Fig. 1 of the drawing, the system shown comprises aplurality of suitable suppl v-circuit conductors respectively markedTrolley and Ground; a plurality of main dynamo-electric i'nachinesrcspectively having armatures A1 and A2, main field windings F1 and F 32and auxiliary or commutating field windings (,1 and C2, all of the fieldwindings being of the cries type; a main-circuit stabilizing resistor Rthat remains in series relation with the main machines during thegreater portion of the operation thereof; a main circuit reversingswitch RS. preferably of a familiar electrically controlled type, asindicated in Fig. 2, for reversing the electrical relations of the mainfield windings F1 and F2 with respect to the corresponding mainarmatures A1 and A2; a plurality of main-circuit switches of awell-known electrically-controlled type LS, l, 2, and 3; amotor-generator or booster set that is provided with threemechanicallyconnected armature windings M, G and E for purposes to bedescribed; a multi-posi-' tion control drum 4 and an auxiliarytwoposition control drum 5 that is adapted to be actuated bv the maincontrol drum 4 under predemrmined conditions; an electricallycontrolledpneumatically operated mecha nism 6 for governing the control drums 4and an over-load trip 'and an over-voltage relay of well-known types forperforming the usual protective functions.

Inasmuch as the main machines are permanently connected in seriesrelation during both the accelerating and the regenerative period, themain field windings F1 and F2 maybe reversed with respect to thecorresponding main armatures, when it is desired to operate the vehiclein a reversed direction, by employing only a single'set of contactmembers on the reversing switch in lieu of the duplicate sets that areusually required in prior system's, wherein the familiar serial-parallelcontrol is utilized. Although the reversing switch is preferably of awell-known electrically -controlled type, as stated above, for the sakeof simplicity and clearness, we have illustrated the reversing switch ina conventional manner and it will be understood that any suit able typeof reversing device may be employed.

The motor-generator or booster set comprises the previously-mentionedarmature windings M, G and E, which correspond to initial operation as adriving motor, as a generator for supplying energy to the main motorsand as an auxiliary exciter for the main field windings. The auxiliaryarmatures may be mechanically connected in any suitablemanner, as by ashaft 10. The auxiliary motor armature M is permanently connected inseries relation with the main motors, while the generator armature G isinitially connected across the main machines and, at other times, isconnected directly to the supply-circuit conductors, as hereinafter setforth in detail.

Although the auxiliary armatures M and G initially operate as a motorand as a generator, respectively, during the latter period of theaccelerating period and the iliary generator armature G is establishedfrom one brush 11 thereof through conductors 12, 13, 11, 15 and 16 tothe highervoltage terminal of. the main armature A1,

.the circuit being continued through the main armature A1, commutatingfield winding C1, stabilizing resistor R, switch 3, when closed,commutating field winding C2, main armature A2, switch 2, when in closedposition, the actuating coil 18 of the limit switch 8, conductor 19,control fingers 20 and 21 which are bridged by contact segment 22 of theauxiliary control drum 5, conductor 23 and series field winding 24 tothe other brush 25 of the armature winding G.

The permanent connections of the exciting armature winding E arecompleted from one terminal 26 thereof through conductor 27, the switch3 in its closed position, the main-circuit resistor R, conductor 28,certain contact members (not shown) of the main circuit reversing switchRS, conductor 29, main field winding F1, conductor 30, main, fieldwinding F2, conductor 31, other contact members (not shown) of thereversing switch RS and conductor 32 to the .negative terminal 33 of theexciting armawhich is connected through conductor 35 to thepositively-energized conductor 1i and the other terminal of which isconnected, through conductor 36, an initially short-cir-- cuited portionof an auxiliary resi r 37, control fingers 38 and 39, which are bridgedby contact segment 40 of the control drum 4, and conductor 41 to thenegative supplycircuit conductor Ground.

In' addition to the seriesrelated field winding 2% for the auxiliarygenerator armature G, a separately-excited field-magnet winding 42 isprovided, one terminal of which is connected, through conductor 43, tothe conductor 13 and the other terminal of which is connected throughconductor 44, control fingers l5 and 1:6, which are bridged by contactsegment $7 of the auxiliary control drum 5, conductor 48 and a portionof the resistor 37 to the negative conductor Ground, as already traced.The exciting armature winding E is provided with a sep arately excitedfield-magnet winding 49, one.

' through conductor 51 and an auxiliary variable resistor 52, to thenegatively-connected 7 control finger 38 of the main control drum 4. Theauxiliary control drum 5 is shown as provided with a rack member 53 thatis adapted to mesh with a pinion member 54 which has an irregulararrangement of teeth and is adapted to be operated through "the agencyof a projection or tooth member 55 of the main control drum 4 when thelatter is moved ZEIOHIPOSltIOII f to position 9 or vice versa. In thisway, the auxiliary control drum 5 is actuated from its normal or initialposition 7 to its other positions 9: It will be understood that theillustrated mechanism for effecting the desired interoperation of'thecontrol drums 4 and 5 may be of any suitable type other than thatillustrated. I

The main control drum 4 normally occupies an initial position a and isadapted to successively operate through positions I) to p, inclusive, inaccordance with the subsequently described actuation of the operatingmechanism 6. The chief function of the main control drum 4 is to varythe active circuit values of the resistor 37 to correspondingly energizethe various separatelyexcited field windings 34, 42 and 49 of thebooster set but is also provided with other contact members orelectrical interlocks, not all of which are illustrated, for the purposeof governing certain auxiliary circuit con nections, as will be setforth in connection with Fig. 2.

The function of the auxiliary control drum 5 is the manipulation of themain-circuit connections of the auxiliary motor armature M and theauxiliary-circuit connections of the auxiliary generator armature G andthe separately-excited field winding 42 therefor, in a manner to bedescribed. As previously mentioned, the auxiliary control drum 5occupies its position f whenever the main control drum 4 occupies any ofits positions a to f, inclusive, and assume its other position gwhenever the main control drum 4 is operating through any of itspositions 9 to p.

T he operating mechanism 6 is of a familiar electrically-controlledpneumatically-actuated type and comprises a pinion 56 that is secured toone end of the shaft 57 of the main 39 and 60 are respectively attachedto operagency of a coil marked On, is fluid-pressure admitted, from theabove-mentioned source, through a pipe or passage 66, to the operatingcylinder 62. The other valve 63 is provided with an actuating coilmarked Off for moving the valve to its other position whereinfluid-pressure is exhausted from the cylinder 61 to the atmosphere.

Assuming that the operating mechanism 6 occupies the position shownwherein the pinions 59 and 60 are biased to their extreme right-handposition by reason of the unbalanced fluid-pressure conditions in thecylinders, the operation of the mechanism 6, without regard to theelectrical connections effected by the associated control drums 4 and 5,may be set forth as follows: To produce a forward movement'of the maincontrol drum 4, the two actuating coils On and Off are simultaneouslyenergized, whereupon, fluid-pressure is admitted to the cylinder 62 andis exhausted from the other cylinder 61, in accordance with theabove-mentioned operation of the valves 64 and 63, and the pistons 59and 60 gradually move toward their extreme left-hand positions.

To effect a stoppage of the control drum. movement at any time, it ismerely necessary to decnergize the off actuating coil, whereuponbalanced-pressure conditions obtain in the two operating cylinders andthe controller movement is effectively and reliably arrested. In actualoperation, the energization of the off coil is controlled by the limitswitch 8, as set forth in detail in connection with Fig. 2.

To return the control drum 4 toward its initial position a, bothactuating coils on and off are decnergized, whereupon fluidpressureconditions in the two operating cylinders revert to the originalunbalanced state and the mechanism is actuated toward the illustratedposition.

The auxiliary relay device 7 is provided with an actuating coil that isenergized or denergized in accordance with the subsequently describedoperation of the coasting relay 9 and is provided with cooperatingcontact member 71 for controlling the energization of the on actuatingcoil, under predetermined conditions to be set forth.

The coasting relay 9 comprises a magnetizable core member 72 ofsubstantially inverted U-shape, having a pair of arms 7 3 and 74 aroundwhich are wound suitable energizing coils75 ad 76, respectively, whichare energized in accordance with the supplycircuit voltage and thecombined main-machine voltages, as about to be set forth in detail. Anoscillatable rod-77 is adapted to freely swin between the arms 73 and 7of the coastlng relay 9 and is normally held in an intermediatesubstantially central position y by means of suitable centering springs78. The rod 77 is provided, near its lower end, with an insulatedcontact member 7 9 that is adapted to engage the one or the other of apair of stationary contact members 80 and 81 when the rod is actuated toits extreme positions as and 2, respectively, for governing theoperation 'of the controller-actuating mechanism 6.

An energizing circuit is completed from the positive terminal of thebattery B through'conductors82 and 83 and a flexible conducting member84 to the contact member 79 of the coasting relay 9. The circuit of theactuating coil 75 of the coasting relay is established from the trolleythrough conductors 84 and 85, the actuating coil 75 and conductor 86to apoint intermediate the switch 2 and the actuating coil 18 of the 'limitswitch 8. The voltage impressed upon the actuating coil 7 5 is thus, atall times, substantially equal to that portion of the supply-circuitvoltage which is applied, or is capable of application, to the mainmachines. The other actuating coil 76 of the coasting relay 9 isincluded in a circuit that is completed from the higher voltage terminalof the main armature Al through conductors 16, 15 and 87, the actuatingcoil 76, and aux iliary resistor 88 which, is adapted to be ishort-circuited by an interlock 2-out (see also Fig. 4) for a purpose tobe described, and conductor 89' to the lower-voltage terminal of themain annature A2. Consequently, the voltage impressed upon the actuatingcoil'76l is, at all times, substantially equal, or directlyproportional, to the voltage generated by the series-connected mainmachines. 4

The purpose of the resistor 88 may be described as follows: Duringcoasting periods of the motors, switches l and 2 are 0 en to disconnectthe main machines from t e supply circuit, in order to reduce theheating of the main field windings F1 and F2 as much as possible andstill maintain the system in a condition of instant readiness to performeither accelerating or regenerative operation in accordance with thesubsequently described governing action of the coasting relay 9, theauxiliary field-circuit resistor is increased in active value by reasonof the removal of a short-circuit of a portion of the resistor by aninterlock 2in, (see also Fig. 4) and Y the voltage supplied by theexciting armature E to the main field windings F1 and F2 is accordinglyreduced. In order to when the maln-circult.

maintain the equilibrium of the oscillatable rod 77 of the coasting rela9 under the changed conditions, the auxiliary resistor 88 is shortcircuited by the interlock 2out, and thus, the effective currenttraversing the actuating coil 76 of the coasting relay is substantiallyequal to the corresponding value, if the main-motor field windings werefully energized and the resistor 88 were active, and the operation ofthe coasting relay is thus not changed by the reduction of current inthe main-machine field windings.

Broadly stated, the function of the coasting relay 9 is to maintain thevoltage of the series-related -main machines, during the coastingperiod, at a value that corresponds, at all times, to the supply-circuitvoltage and thus compensate for changes in vehicle speed by reason oftraveling upor down grades or around curves, so that the instant thetrain operator actuates his master cont-roller (see Fig. 2) to any oneof its positions Brake, Hold or Run, the corresponding main-machineoperation will begin, with practically no time element of the motors orother portions of the system and without any surge of current to or fromthe supply circuit. Of course, the voltage of the auxiliary excitingarmature E and, consequently, of the main field windings must beincreased from the relatively low values employed during coasting; butsuch action takes place almost instantaneously upon the closure ofswitch 2 and the resultant reshort-circuiting of a portion of theauxiliary field-circuit resistor 52. The time lag of the selectedaccelerating or regenerative machine action behind the movement of themaster controller is, therefore, negligible.

The automatic action just outlined, which may be termed as anticipatoryof any subse quent action of the train operator, is accomplished bymeans of the control of the on and the off actuating coils of theoperating mechanism 6 through the a ency of the cooperating contactmembers, 9, 80 and 81 of the coasting relay.

For example, assuming that the main motors are coasting on asubstantiall level track or up a slight grade so that tie machine speedgradually decreases, or assuming that the supply-circuit voltagesuddenly increases, then the action of the machinevoltage-actuating coil76 of the coasting relay will decrease in either actual orrelativestrength and the consequent predominance of the other actuating coil 75will cause the oscillatable arm 77 to assume its iosition ac, whereupona circuit is completed from the positively-energized contact member 79through control finger 80, the actuating coil of the auxiliary relaydevice 7 and con- .ductor 90 to the negative terminal of the battery B.The auxiliary relay device 7 is thus actuated to its upper orinoperative III - predominates members 71 of the relay device 7interlock lout, the purpose of which will be described in connectionwith-Fig. 2, conductor 91, the actuating coil On and conductor 92 to thenegative battery terminal.

The consequent deenergization of the on actuating coil in conjunctionwith the action of the already deenergized other valve 63 causes animmediate return of the main control drum 4 toward its initial positiona to thus, for example, gradually decrease the voltage of the auxiliarygenerator armature G and simultaneously.increase the electromotive forceof the auxiliary motor armature M which is connected in series relationwith themain machines, and thereby produce a condition in the systemthat corresponds to a substantial balancing of the supply circuitvoltage with the generated voltage of the main machines 'in conjunctionwith the series-related auxiliary armature M, whereupon the forcesexerted by the two actuating coils 75 and 76 of the coasting relay 9 areagain balanced and the oscillatable rod 77 assumes its intermediateposition.

On the other hand, if the vehicle strikes a down grade, for example, orif, by reason of supply-circuit voltage fluctuations, the gem-matedvoltage of the main machines, while coasting, rises above the propervaluewith respect to the simultaneous supplycircuit voltage value, .thenthe machine-volt age-actuating coil 76 of the coastin relay over thesupply-circuit-voltage-actuating coil 75 and the oscillatable arm 77- ismoved to its extreme right-hand position a to complete a circuit fromthe positively-energized contact member 79 of the relay through controlfinger 81, conductor 93, cooperating contact members 94: of the limitswitch 8 in its lower position,

conductor 95, the actuating coil oil and conductor 96 to the negativeconductor 92. Thus, the off actuating coil is energizedsimultaneouslywith the already normally energized actuating coil On anda movement of the main control drum 4 toward its final operatingposition p occurs, whereby the energizations of the several fieldwindings of the booster set are varied to effect a reduction of thevoltage generated by the coasting main machines until balancedconditions again obtain, whereupon the oscillatable arm 77 of thecoasting reay again assumes its intermediate position.

Consequently, the coasting relay 9 automatically compensates for thechanges in grades or curves of the track and also for the unavoidablefluctuations of supply-circuit voltage and maintains a balance be-.

previously com- Brake,

tween the generated voltage of the coasting main machines and the supplycircuit at all times, to permit the above-mentioned substantiallyimmediate response of the machine to the operation of the mastercontroller to any of its operative positions.

The over-voltage, relay may be of any suitable type and, as illustratedin Fig. 2, is adapted to open the main-circuit switch 2 underpredetermined abnormally high-voltage conditions, whereby the mainmachines and the booster machines are prevented from building up anexcessively high voltage, through dynamic braking action, which wouldtend' to injure or destroy the various machines, by flash-over troubles,or otherwise, as will be understood.

Reference may now be had to Fig. 2 Whiz-1. illustrates, in addition tothe various actuating coils and the auxiliary contact members of therelay device that are shown in Fig. l, a master controller MO that isadapted to occupy an off position and a plurality of operative positionssrespectively marked Hold and Run for correspondingly governing themain-machineoperation; a master reverser MR of a familiar type forgoverning the actuating coils f and r" of the main-circuit reversingswitch RS; a plurality of train line conductors TL for connectingvarious auxiliary circuits with the master controller and for adaptingthe system to multiple-unit operation, in

accordance with a familiar practice; and

mterlocks or con- 1;:

a plurality of electrical tact members of a well-known type that areillustrated in connection with the switch 2 in Fig. 4. Since theinterlocks just mentioned are old and familiar in the art, no

further description or illustration thereof is believed to be necessary.

The supplycircuit switch LS is not governed by the master controller,but is normally closed at all times in accordance with a circuit that is(see Fig. 3) through a suitable cutout switch 100, a control resistor101, the auxiliary contact member 102 of the overload trip which thuscontrols the connection of the main machine to the supply circuit, theactuating coil of the switch LS, conductor 103, switch interlock LS-outand 1out,

interlock al-a of the main control drum 4 in its initial operativeposition a, and conductors 104 and 105 to the negative supplycircuit'conductor Ground. Upon the closure of the switch LS, a holding circuittherefor is completed from the conductor 103 through an auxiliaryresistor 106, whereby the current consumed by the actuating coil circuitof the switch LS is reduced during the time. that the switch is closed,interlock 107LSin and conductor 108 to the negative conductor 105.

Assuming that the supply-circuit s itch completed from the trolley LS isclosed and that the various portions of the apparatus occupy thepositions shown in Fig. 1 and Fig. 2, the acceleration of the mainmachines may be effected by actuating the master-controller MC to itsfinal operating position Run, whereupon a circuit is completed from thepositive terminal of the battery B through conductors 110 and 111,control fingers 112, and 113, which are bridged by contact segment 114of the master controller, conductor 115, control fingers 116 and 117,which are bridged by contact segment 118 of the master reverser in itsforward position, conductor 119, train-line conductor 120, conductor121, contact member 122 of the main reversing switch RS in its forwardposition, conductors 123, 124 and 125, where the circuit divides, onebranch including conductor 126, the actuating coil of the switch 1, andconductor 127, and the other branch including interlock 4 -a, conductor128, the actuating coil of the switch 3 and conductor 129, whence acommon circuit is completed through conductors 130 and 131, train-lineconductor 132 and conductor 133 to the negative terminal of the batteryB.

Another circuit is simultaneously established from the contact segment114 of the master controller through control finger 134, conductor 135,train-line conductor 136, conductor 137, cooperating contact members 138of the overvoltage relay, the actuating coil of the switch 2, conductor139, interlock 9-g of the coasting relay 9 in its intermediate orneutral position 3 and conductor 140 to the negative conductor 130. Thepurpose of the interlock 9- 1 is to prevent the switch 2 from closingunless the previously mentioned balanced-voltage conditions obtain withrespect voltage and the generated voltage of the main machines duringthe coasting period. Upon the closure of switch 2, a holding circuittherefor is formed by the bridging of the interlock 9-1] by an interlock2-in.

Referring temporarily to Fig. 1, the main circuits completed by theclosure of switches 1, 2 and 3 may be traced as follows: from thetrolley through the actuating coil of the overload trip, switch LS,conductor 141, switch 1, main armature A1, commutating field winding C1,stabilizing resistor R, switch 3, commutating field winding C2, mainarmature A2, switch 2, the actuating coil 18 of the limit switch 8.conductor 19, control fingers 20 and 21, which are bridged by thecontact segment 22 of the auxiliary control drum 5 in its position 7',

conductor 142, series field winding 17 and auxiliary armature winding M,conductor 144, control fingers 145 and 146. which are bridged by contactsegment 147 of the auxiliary control drum 5, and conductors 148, 149 and150 to the negative conductor to the supply-circuit.

Ground. The initial main-circuit connections are more simply shown inFig. 5.

In the initial operating position a of the main control drum 4, theresistance of the circuit of the field winding 42, which corresponds tothe generating armature G, equals its maximum value by reason of therelation of the resistor 37 to the movable contact members of the maincontrol drum 4. On the other hand, the energization of theseparately-excited field winding 34 for the auxiliary motor armature Mis at its maximum by reason of the direct connection of the fieldwinding through the contact members of the main control drum 4 to thenegative conductor Ground.

Under the starting conditions just outlined, the auxiliary motorarn'iature M absorbs substantially all of the supply-circuit voltage andthe main machines are thus gradually started into operation as thevoltage of the armature M is decreased by reason of the actuation of themain control drum 4, which actuation simultaneously increases thevoltage of the auxiliary generator armature winding G, the same resistor 37 being employed for the increasin and decreasing actions justmentioned The excess of energy over that actually required by thevarious main and auxiliary machines is returned to the supply circuitthrough the agency of the generator armature winding G.

To effect the forward operation of the main control drum 4, one circuitis completed from the contact segment 114 of the master controller MC,through control finger 151,,conductor 152, train-line conductor 153,conductor 154, actuating coil 155, of a relay device marked Regen. relayand conductor 156- to the negative conductor 131.

The actuation of the regenerative rela to its upper position completes acircuit rom the conductor 15.4, through conductor 157, cotiperatingcontact members 158 of the relay, conductors 159, 160 and 91, theactuating coil On of the main control drum 4 and conductor 92 to thenegative conductor 130.

In addition to the function just described, the regenerative relay isadapted, in its upper position, to remove a short-circuit from a portionof the auxiliary resistor that is included in circuit with theseparately-excited field winding 49 of the exciting armature E (see Fig.1). Thus, whenever, the master controller occupies its positions Run orHold, the regenerative relay occupies its upper position, and theencrgization of the field winding 49 of the exciting armature E iscorrespondingly reduced by the insertion of a portion of the resistor52. On the other hand, whenever the master controller occupies itsposition Brake. the regenerative relay is deenergized and drops t v iseparation; of'jcont-rol finger "165, :WhiClIlS :di rect-ly 'connectedto' the separatelyexcited rent:

ductor 162, 'trainlineconductor 163, conductors 16a and 93, thecooperating contact members 94 of the limit switch'8, conductor 95, theactuating coil Ofif? of the main control drum land conductor96 to thenegative conductor 130.

I Since both actuating coils-of the operating mechanism't aresimultaneously energized, the main control drum at will-move forward inaccordance with the'positionof the limit switch 8, or, in other .words,will maintain a substantially constant accelerating cur- 1 The forwardoperation at; the main-icon- --field-'magnet winding 34' forzth armatureM of the boos teir set; ttromucontact segment -166-of -the ma inoontrolpdrum t, while-an additiofiaP-Contiol finger, which is connectsetforth. One result-of this actuationof the auxiliary drum v 5 is J tocomplete. a; circuit from the series field winding 2% of the auxiliarygenerator armature Gr througlnconductor 23, .controlfinger 21,-conductor.ll68,

' control-finger 169,contact member l4r7and conductors 148, 1&9 -an dl50 to the negative conductor Ground," whereby the auxiliary generatorarmature-G andwits,series tield M eddir ly, asipss the. pp yicircuit. iu

, Another change impact-nation ot' .th'e auxiliary control; druni '5stoits posithrough conductor 19, control finger 20; and

contact segment :ofithe control drum 5,

:-=c'onduc tor 170, contact segment L71, control I'finger:v 145,conductor 144,;- the ;auxiliary =motor-armature1H,;series field winding17 conductor-142 and thence through; conductor 168, asi j nst tracedgout, Thus, :the auxiliary g IIiOtOI' armature M and its jseries gfieljd;157, are I momentarily short-ciroiiitediwhen thelmolttrol drum to-its'FsecondZposition ,b-:etfects--.the V age I thereote-is-,rnegligible ,and a fet then. re, ,90

Asstill-further cliangemttci rcgi its isggcgomplished; atithistimetbylreasonof tie ,connecfield winding 42 foi tlie auxiliarygenerator ed toanother; intermediate point of the resistor 37, 'engages' contactsegment!l66.- A certain section of the resistor 37 is: thus in cluded incircuit with the field winding 34:

for'the annature; M whereas, the same sectlOIlj'lS'SlIDlIlltfil'IOllSlY.excluded from the circuitof-the separately-excited field windwinding'GJSimilar results obtain from the ing 42 for the auxiliaryigeneratorarmature step-by step movement ofthe main control drum its position f,Whereinthe resistance-i'n circuit with the generator field winding42 iscompletely"short circuited and; a maximum section of the resistor 37is-included in circuit with the motor field winding34. ThUS- -'th8voltage of the auxiliary motor armature Mis reduced to subst-an- 1.tially' zero in a gradual manner and, simultaneously, the voltage ofthe generatordanmature G and of the parallel circuit-comprising the twomain machines, is increased to substantially --supply-circuit voltage,so

600 volts, approximately 300 volts is imsponding to full-seriesoperation of the motors in the customaryseries-parallel control system.

As the main control drum 4 is moved from position-f to position 9, nocircuit changes are efiected thereby, but the auxiliary control drum 5is actuated to its other position 9 by means of the rack-and-pinionconnection between the two drums, as hereinbetore armature Gr throughconductor 4st, cont-r01 fingers t5and 172,,vvhich are bridgedby contactsegment 4710f theauxiliary control across the supply-circuit Thus, theauxiliary generator armatu e 5 G from this time on-throu'ghoutacceleration acts as a substantially;constant speed motor fordrivingthe. auxiliary armature iM asl a negative booster to supply; angraduallyincreasing electromotive-force that, isjbelow the potential of thenegative supply;ci rcuit= t conductor Ground,- and also. ion-driving'the excitingarma-ture E. ,;-z; t;. fi s;

As the main-control-drum t,.-is(actuated through positions;-h;to Z,inclusive,-. ,the;;r e versed action of-the resistor 37,- withrespect tothe auxiliary :moto'r anmature M i 1- f- "that, assuming asupply-circuit voltage of v fected, that is to say,-; thei-resistorgisgradually excluded from thetcirc-uit ofatlie separately excited fieldwinding 34: forthe'auxiliary. armature M until in position l,-maxipressed across each main machine, corremum excitation thereot againoccurs as; was the case in position (1.; At; this time,-.therefore, thevoltage oft-he armature issub- I stantially equal and; in thesame-direction Wltll: the supply-circuit voltage ,so that, in

impressed from the-auxiliary armature M upon the other Inamunachme, thusgivinga io ;tionvof one terminal of the separately excited .drum 5, andconductor 173. to.;tl1e ,;negative-,; 00 conductor 150, wherebytheLseparately-excited field winding-42 itlsnconnected directly theequivalent ofa full-parallel connection in a system of the familiarseries-parallel type. i i

the separately-excited field winding 49 for the exciter armature E isgradually 'decreased by reason of successively including section of theresistor 37 in circuit therewith through the agency of control fingers174 and the contact segment 166, and thus the excitation of the mainfield windings F1 and F2 is correspondingly gradually decreased toproduce the well-lmownnresults of-field control, namely, a highermain-machine speed.

The weakening of the main field-winding excitation is continued inposition 1) of'the main control drum 4 by the opening ofthe switch 3,whereby the 'stabilizin -resistorZ R is open-oircuited' and the' rhainfie d windings F1 and F2 are connected-in straight series relation withthe corresponding -maimarmature windings, the proportion offpartsibeingsuch that the opening'of the switch 3'1efi'ects a suitable decrease-ofthe'fcurreiititraifersing 'the main field windings and thus producesthedesire'dresult of increased speed-m The opening of the switch 3isfeife' ted y reason of the disengagement of afwcontact member 4-11),to '0 fromthe-corresponding V auxiliary controlfingers ofthefm'aincontrol drum 4, such'connection having beenimaintainedfrom theposition b to theposition: 0 by reason of the completion of acircuitzfrom the positive terminal of the vbatteryihB through conductors110 and '175,' trai n-'line conductor 176, conductors- 17 7 and 17 8, tthe interlock 4- 2) to a; and conductors 17 Band 128 to the actuatingcoil of the switch 3. The closure of the switch 3 and the consequentenergization ofthe'main field windings F1 and F2 from the excitingarmature E is thus insured during the coasting period of the mainmachines, -irrespecti've of the operation of the master controller;

Regenerative operation is obtained by I merely operating the maincontrol drum 4 through its positions p to a, inclusive, or, in otherwords, by exactly'reversing the ositions that were employed during acoeerating operation. The initial regenerative main-circuit connections areillustrated in a simplified manner in Fig. 6.

I In'general, the main field winding is connected in circuit with theauxiliary exciting armature E and the stabilizing resistor R, the fieldexcitation of the exciting armature is strengthened to compensate for apredetermined decrease of main-machine speed, the voltageof theauxiliary armature wind ing M,'acting as a generator, is graduallyreducedto zero while the remaining'auxiliary armature winding G. actingas a motor, is connected across the supply circuit, the armature windingM 1s then reversed In positions m, n and o, the'ener ization of and actsas a motor to gradually absorb in- "oreasing amounts of thesupply-circuit voltage, while the armature winding G is connected, as agenerator, in parallel relation to the main machine, until the'speedthereof decreases to substantially zero and the auxilia-ry armaturewinding M absorbs substantially the entire supply-circuit voltage, whichoccurs when the main control drum 4: reaches its position a. Inasmuch asthe regenerative operation of the system is exactly the'reverse of theaccelerating operation, it is not. thought necessary to describe theregenerative operation in detail.

However, a brief exposition of the operation of the main controllingdevice ,1 will The given. During regeneration, the regenerative'rela'yoccupies its lower position by reason of thedenergization of conductor25154 when the'mastervcontrolleriis moved to the brake pos'ition. Theenergizing circuit of theiionl actuating coil is then completed fromconductor 12%, through cooperating 'contact'members 185 of the limitswitch 8 in itsilpperfposition toconductor 160; Since theifoflactuatingcoil is energized through thecontact members 94: of thelimit'switch =-:8 in--its loweripositionpit follows that the necessaryvsimultaneous denergization of .ithe'two coi'ls,=in q'uestion to effectbackward -..-step-by-step movement of the control drum --:-'.4, "asthemain machine speed decreases, is

eldependentcupon the intermittent action 0? the limit switch.

Furthermore, the function of the contact member or interlock lp that isconnected in circuit with, the actuating coil of the switch'2'will beexplained. In case the vehicle is coasting, and,.byreason of travelingdown a grade, attains a speed that is higher than-the-normal speed thatcorresponds to the final gaccelerating position p of themaincontrolxdrum 4, then the coasting relay9 will automatically act toenergize the off actuating coil, as previously described, in an attempt'to decrease the generated voltage of :the momentum-driven machines,which voltage, for the time being, pro!- dominates' over thesimultaneous supplycircuit voltage value. Since the main control drumalready occupies its final position. no further movement thereof in thedesired direction is possible and, therefore, the oscillatable arm 77 ofthe coasting relay 9 will remain in its position .2 until the vehiclespeed decreases to the normal maximum value.

A However, if it should be desired to eifect from the circuit of theactuating coil of the switch 2, by means of the completion of thecircuit in question through the interlock '4p, whereupon regenerativeaction begins 1 is in circuit with the auxiliary contact mem- 5 barsfl'of the relay device 7 will now be explaincd. Under accelerating orregenerative ctmditions, the circuit in""question is inoperative byreason-0f the closure-of the switch 1. When the. ma n machines arecoastlng,

l0 however. the interlock 1.-0ut and the auxiliary contact members 71,in the closed posi- -tio n, complete the circuit of the on? actuatingcoil, (whichfis then governed by the coasting relay9, aspreviously setforth.

It will be seen that thereis thus'provided a relatively simple,-effective and reliable control system for. accomplishing economijcalacceleration of a,plurality of permanently series-connected maindynamo-elec- '20 :tl'ic anachines through theagency of a motor-generatoror vhooe ters;Set,- two of, the armature windings of which in tiallyareconnected in series relation with,.a-nd in parallel.

-- fl'elntiol'l tt), the main machines-$95,101 as a r spee ire y; hauxiliary motorarmature then is converted 3:(2Q1116S a drivingmotortherefor. Thus, the

. eql livalent of series parallel? control is obtained,in-1h at the mainmachines eventually have a voltage impressed upon eachof them that ISsubstantially equal to the supply-cirexcitation of an auxiliar -yexciting armature that-is connected to energize ,themain field -40windings. in the samedirection during both -accele at-ion andregeneration, whereby v.no

- .reversal of the main field .windings with respect to the-mainarmature is necessary when passing from acceleration to regeneration orvice versa.--

Broadlystated, therefore, one phase of the herein-describedinventionscomprises a method of operation of a driving unit comprising oneor moremain dynamo-electric machines bygradually impressmg thereon anincreasing proportion of A the supply-circuit voltage, next creatingianelectromotiveforce below thenegative voltage of the supply circuitand.then gradually algebraically subtracting the negative electromotiveforce from thesupply-circuit voltage to thus impress an increasinglyeater effective voltage upon the main-mac ines:

Stated another way, the initial acceleratmg connections employthe'supply-circuit conductors as a two-wire circuit, and subsequently'the equivalent of a three-wire system is created that utilizes thenegative bility of such conditions, the main machines as the neutralwire.

to a generato yofelectl'O-motivejorce below the negat ve volt age' -o fthe 1 supply; circuit, while the; former 'ai xiliary, generator be lows:Although during the latter part of the accelerating period and the firstportion of the regenerative eriod,,the equivalent of l200 -voltoperation s obtained, yet the voltage between any part of either motorand the negative or ground voltage isnot more than (300 volts. Thus themachines need to be insulated to withstand only the latter po-'.tential, or, in other words, the machines may be of the standard(SQO-volt type.

It is estimated that the total capacity of the three booster armaturewindings need. be approximately only 75% of the combined capacity of the111ain' nachines,by reason of the fact that the current in the auxiliaryarmature winding "ll'i varies between zero and the main machine current,the average current carried by the auxiliary arauature G issomewhat-less, andthe current lYhereas, thefp or ,'regenerative systemswherein a separately-excited field wind ng alone is employed, arecapable of regenerating down to about 8.0r 10. miles per hour, the.

.present systenr will permit jregeneration. to -substant1ally zero.speed. Moreover, the rhcostatic losses occurmg 1n the usual motorcontrolsystem ,are practically eliminated. and the present control system, ingeneral, is less complicated and, therefore,less expensive in first costand maintenance than prior fully automatic'. regenerative systems ofwhich wehave any knowledge.

It will be understood that various modifications 'in the above-describedsystem may be effected without departing from the spirit and scope ofthe herein-described inventions.

'For example, ifdesired, the field winding, instead of thearmaturewinding of the auxiliary armature M, may be reversed to effeetthe desired negative booster action and the field excitation of theauxiliary armature winding G may be varied when the armature is actingas a driving motor. Moreover, as is wellknown, in regeneraeducing theactual tive operation during relatively high mamay initially beconnected in parallel relation during the regenerative period and be andR. E. Ferris, Serial -No.' 59,992, filed 'ing' a movable control membeibperath under predeterminedmachine "conditions for staiit readiness toeft'ect'iitherselected op'e'i'.

" V n w raw ilnif 9 viith a machine: a regenerative"Operation, ofiiea'iis'*dpei-atii' e' November (3, 1915, and assigned to' the West'-inghousc Electric & hlanntactnririg Company.

It is our intention in the appended claims to cover all themodifications of certain portions of the hereinbefoic-described systemthat rightfully fall within the spirit and scope, of our .presentinvention. '-\Ve claimas our invention:

'1. In a system of control, the combination Withjaisupply circuit and adynamo-electric '-ma' cl ine adaptedfor both accelerating andregenerative operation, of means compris' iaint-aining tlie sys tein iiiIi siibstantially i a .11.. .z,. I control, the-comb nation ly ei'rciit'and a dynamo-electric ap'ted for-"both accel ritiiig aiid in s stemunder coasting conditions of the machine. to maintain a predeterminedratio bet-ween the supply-circuit voltage and the machine volta e,whereby-the system finiaintained in su istantially instant readiness toefiieet' either acceleration orregen'e 'atioii. ance-1c. machine adaptedfor both accelerat- 3. Ina system of control, the combination with asupply circuit and a dynamo-electric machine adapted for bothaccelerating and regenerative operation, of means forgovern-f ingcertain circuit connections during ina-' chine operation, and means formaintaining said governing means in readiness to effect substantiallyimmediate accelerating or reenerative action of the machine. J

4. In a systein of control. the combination with a supply vcircuit and-a dynamo-electric machine adapted for both accelerating andregenerative operation, of incans dependent upon relativeconcurrent-values of supplycircuit voltage and machine voltage for orregenerative opera ti on.

O. In a system of control. the combination with a supply circuit and adynamo-electric in'achinc adapted for both accelerating and regenerativeope 'ation, of means operative under coasting conditions of the machinefor inaintaing the system in substantially iiistant readiness to efi'eetregenerative operation. 7. In a system of 'control, the combination with'a supply circuit and a dynamo-electric machine adapted for bothaccelerating and regener'z'iting operation, of means operative undercoastingcon'ditionsof the machine to maintain a predeterinined'iatiobetween the 'supplycir'cuit' voltage and'th'e machine voltage, wherebythe' system is maintained in substantially instant" readiness to-efi'ect re- "generativeoperation; v I 8-."In' a system bf coiitrol, thecombination with asnp i'lv circuit and a dynamo-electric macliiiiefadapted for both accelerating and --regenerative operation, ofaii'eansdependent ii'pon'irelati-ve"concurrent values of supply- 4 -volta,,e'aiid 1nacliinVolta e for maintaining-the syst m in substantiaily inp{Wetter-t regenerative opera- 2 flan- :1; new e 'Hii system ofcontrol;the combination itli a'isnppll circiiitaii'd a d nani o electric'niacli'l'iie a'da te'd for both acceleratingand perat-ion, of"ii'ieans'operati ve -in accordai'ie \v'iith tlie" machine speed forinaintainiii'gth'esystem in substantially ins "to effect regenerativeoperamii,

mg :and regenerativc- -opei"ation,--"of means for govern'ini certaincircuit connections during machineoperation, and ineans for maintainingsaid governingnicans in i-eadiness' to' effect substantially immediatercgenerative actionoffthe machine.

11. 'Zlii a system (if-control, the combination with a supplv circuitanda dynamo- -electric machine adapted for both accelerating andregenerative operation. of a controlling device governing the excitationof the main machine, and ineansfor manipulating said'conti'ollingdeviceiunder coasting conditions of the machine -to"'in'aintain thegenerated voltage thereof in snch proportion to the conciu'rentsupply-circuitvoltage that substantially immediate regenerative actionof the machine may be affected at any time.

1'21 In a system of control, the combination with a supply circuit and adynamoelectric machineadapted for both accelerating and i'egeneiaitiveoperation. of a multiposition controlling device governing theexcitation of the main machine. and means for efi'cctiug the actuationof said device in the one or the other direction in accordance withvariations of machine speed to main 35 supply-circuit voltage thatsubstantially im- 13. In a. system of control, the comhina-.

tion with a supply circuit and adynamoelectric machine adapted for'bothacceleratmg and regenerative operation, of a multiposit-ioncontrolling device governing the excitation of the main machine, andmeans actuated in accordance with the relative concurrent values ofsupply-circuit voltage and n'rachine "oltage t0 efl'ect theoperation ofsaid device in the one or'tlie-other direetion to maintain the generatedmachine voltage in such proportion to the concurrent supply-circuitvoltage that substantially immediate regenerative'action of the machine;

may be eifected at any tin'ie v 14. In a systcm of eontro he combinationwit-ha supply" circuifiandfa dynamo- I electric machine adapted for'hoth'aceeleratwfefiected at anytime.

ing and regene 'atiye operation, of a-m'ultr position controlling devicegovern ng the exeltatlon of the mam machine; an electri cally controlledmechanism for' operating-- said device, and relay means actuated incally-cont'rolled mechanism to effect-movein such proportion to theconcurrent supply-circuit voltage that substantially immediateaccelerating or regenerative action of the. machine may be selectivelyobtained at any time.

17. In a system of control, the combination with a maindynamo-electricmachine adapted forboth accele 'ating and regenerative operation, of'aplurality of auxiliary machine armature windings respectively connectedin series relation with and in parallel,.relation to, the main machine,controlling means for governing theexcitat-ion of the auxiliary machinesto effect operation of the main machine, and means for eflecting theactuation of said controlling means in the one or the other direction inaccordance-with; variations,of-{machine speed to maintain the-generatedmachine voltage in such proportion-to the-supply-circuit voltage thatsubstantially,innnediate regenerlative "actlon'of' the main machine maybe 18. In a-system of control, the combination with 'ai-mamdynamo-electric machine -ada'pted for both acceleratingand'regencrativer-operation, :of a plurality of auxiliary machinearmaturewandings respectively connected in series relation-with and inparallel-relationato, the main machine, andin cn'cmt with themam-machine field winding,

a controlling device for governing the exciment, the 'eqfinthe qne 01'the-,dthr dir .'z-ttation G ft-the auxiliary machines t0 effect tion "toniaintain" the generated machine voltage 111 such proportion to theconcurrent mediate"regenerative action of the 'inachin 3 may beefi'ectedat any time. 1

electric machine adapted for both"' z'ic'celer position controllingdevice governing the chine may be 'efi'ected at :any time.

excitation of the main niachi'ne, and means.

for effecting the actuation of said device in the one or the otherdirection in accordance" with *ariations of machine speed to maintainthe generated machine voltage in such proportion to theconcurrentsupplyfcircuit voltage that substantiallyimmediate accclcrating, or regenerative action of the machine may he :-'0lectivelyohtained at any time.

16.'In""a systcm of control, tliec01 ubina-* to' maintain the generatedmachine voltage 19.: In a system of control, the combina- 'tion with amain dynamowlectric machine adapted for both accelerating and regeni'erative operation, of a plurality of auxiliary machine arnniturewindingsrespectively connected in series relation with, and in parallelrelationto. the main machines, controlling means for governing theexcitation of the auxiliary machines to eifectoperation ot' the mainmachine, amaster controller for nor inally governing the :main-machineconnections and said controlling means and adapted to occupy an of, arun and a brake position, and a relay device operable when the mastercontroller occupies its 01f position andthe main machine is coasting toefiect the actuation of said controlling means in the one or the otherdirection in accor lance with variations of machine speed to maintainthe; generatedmachine voltage in suchproportion to the supply-circuitvoltage nections and said controlling means andadapted to occupy-"an'off; afrun? and a brake position, and ai relay (163N106 -oper.-. 2.

tive operation, of a plurality of auxiliary machine armature windingsrespectively" connected in series relation with,- and in par- I allelrelation to, the main machines, controlling means for governingthe-excitation of the auxiliary machines to effect operation of the mainmachine, a mastercontroller for normally governmg the main-machinecon--.

able when the-master controller occupies its ofi' positionand the main-m'acl1ine is tively.

coasting to eflect: the actuation of said 00111::

trolling means in the' one or the other direoei I tion in accordance'with .the relative concur-,.

rent values of supply=c1rcu t voltageand -mach1ne voltage to maintainsaidas'oltageslnrjamalmclrcuitswitching device irrespective of tomaintain a predeterminedratio of saidwvoltages, and interlocking meansfor pre venting the closure .of said main switching device unless saidrelay device occupies its intermediate position.

-23. In a system of control, the combination with a suppl circuit and adynamoelectric machine a apted for both accelerating and regenerativeoperation, of a maineircuit switching device, a multi-positioncontrollingdevice governing the excitation of-the main machine,athree-position relay devicebiased to an intermediate position andactuated to theone orthe other of its outer positions in accordance withthe relative concurrent values of ,supplyecircuit voltage andmachinesivoltages-to;effect the operation of said gcontrolling;device inthe one or the otherdirection to maintain a predetermined ratio of saidvoltages; interlocfking means for 'preventihg'thecclosure of saidmain-circuit switching ,devicejmless {said relay-device oceupies fitsintermediate position, and means operable in; fitgQIitjQjPQSitigg ofsaid controlling deviceto eji'ectsthelclosnre of the suchproportionithat substantia1ly"immedi-::ithe position ofsaidarelayflevice. i

ate acceleratingor regenerative action: of the main machine 'may beeffected at'any :time

upon movementof-wthe master controller to; the run or the brakeposition, respec-. .-.-i,1 1g and regenerative operation of aimain- 1'.-z circui t*sswitchingdevice,iga multi-position system of control,*the1combina-.;- icontrolling device 3 governing the; excitation 21. Ina tion "with a supply circuit and a dynamoelectric machine adapted forboth .accele1fl-- ating and regenerative operation,"of -asmainsi circuitswitching device, awmulti-positionsimachinevoltage 1i controlling devicegovern-ingthe excitation of-the main machine; controlling means for:effecting the actuation of said device in the one or the other directionin accordance with variations of machine speedto maintain the generatedmachine voltage in a predetera =mined ratio to the supply-circuitvoltage,

and means associated with isaidl controlling means for preventing theclosure of said main-circuit switching device unless said ra; tioobtains. 1 Y

22. In a system of control, the combina.-- tion with a supply circuit,and a main dy-. namo-electric machine adapted for bothacceleration andregeneration, of a plurality of 'auxiliar dynamo-electric machines forvarying the applied voltage and fieldwinding excitation of the mainmachine, a main-circuit switching device, a multi--. positioncontrolling device for governing the excitation of the auxiliarymachines, a three-position relay device biased to an intermediateposition and actuated to the one or the other of its outer positions inaccordance with the relative concurrent values. of supply-circuitvoltage and machine voltage to effect the operation of said controllingdevice in the one or the other direction a-. .-2 .I aisys mioi cent 131h? combination with a ,supplv icircuit and Pa dynamo- 1 ct c;:1n a nei dp e lif h,- acce e a 5 of the main machine, 5a a relay device actuatedin accordance ;.with the relative -concurrent values. of gsupply-circuitvoltage and i0 7. .eifecting the actuation of said contro ngdeviceingthe one or the other directionto maintain apredetermined ratioof said voltages under coasting conditions of said machine, a mastercontroller for v normallyagoverning the main-circuit. switching -,dev1ceand the controlling device, and means operable in predeterminedpositions of thes,control ling device for maintaining saidswitchingdevice closed irrespective of the master controller. 25.,In-asystenrofcontrol, the combinati n with, a Supply circuit and adynamo-electric machineadapted for both accelerating and regenerative.operation, of an auxiliary source Ofenergy, a switching device forconnecting said source of energy in circuit with the main machine-fieldwinding, a multi-position controlling-device governing the active valueof said source of energy, a relay device actuated in accordance with therelative concurrent values of supply-circuit volt age and machinevoltage for effecting the actuation of said controlling device in theone or the otherdirection to maintain a predetermined ratio of saidvoltages under coasting conditions of said machine, a master controllerfor normally governing the switching device and the controlling device,

Ill

and contact means operable in nearly allot the controlling devicepositions for rnain taining said switching device closed irrespective ofthe master controller, whereby the niain-field-winding excitation ismain tained during coasting periods.

26. In a system of control, the combination with a supply circuit and adynamoelectric machine adapted for looth accelerating and regenerativeoperation, of an anxiliary source of energy, a switching device forconnecting said source ofenergy in circuit With the main machine fieldWinding, n1ulti-position controlling device governing the active valueof said source of energy, a relay device actuated in accordance with therelative concurrent values of supply-circuit voltage and machine voltagefor effecting the actuation of the said controlling device in the one orthe other direction to maintain predetermined ratio of said voltagesunder coasting conditions of said independent of the controli reviceducing the active va ue cf said source Ola ergy during periods, and.means or correspondingly reasing the said ma chine voltage applied tosaid relay reducing the 9?. in a system of control, the combination witha supply circuit and a dynamo-electric machine adapted for bothaccelerating and regenerative operation of an auxiliary eXciting machinefor the main machine field Winding, a multi-position controlling devicegoverning the field excitation of said auxiliary machine, a relay deviceactuated in accordance with the relative concurrent values ofsupply-circuit voltage and main machine voltage for effecting theactuation of said controlling device in the one or the other directionto maintain a predetermined ratio of said voltages under coastingconditions of the main machine, switching means independent oi thecontrolling device for excitation of said auxiliary machine duringcoasting periods, and means for correspondingly increasing the finachinevoltage applied to said relay 11011} whereof, We have hereunto 1 ournames this 2nd day or Aw

